Vehicular Visible Light Communication Research Articles

Deep learning approach for automatic modulation format identification in vehicular visible light communications

Deep learning approach for automatic modulation format identification in vehicular visible light communications

Non-line of sight analysis for vehicular visible light communication system: Impact of artificial light source and weather conditions

Visible light communication is seen as a crucial technology within optical wireless communication systems. The technology of vehicular visible light communication holds significant importance in the context of connected vehicles. This technology can serve as a supplementary solution to vehicular systems that are based on radio frequency. In this paper, the authors conduct an analysis of the performance of both line-of-sight and non-line-of-sight vehicle-to-vehicle visible light communication systems under the effect of artificial light source and weather conditions, including clear, hazy, and foggy weather. A practical vehicular laser diode, a street lamp, and an avalanche photodiode are used to design the proposed system model. Performance enhancement for the proposed system is achieved using an optical amplifier at the receiving end. An artificial light source of light-emitting diode Corn-type is used to represent an ambient artificial light source. Different metrics such as quality factor and bit error rate are used to assess the system performance of the non-line-of-sight-vehicular communication system. The proposed line-of-sight model achieves a data rate of 25 Gbps, supporting a distance of 80 m under clear sky and hazy atmospheric conditions. For foggy weather, an attainable link distance of 70 m is achieved. The achieved results emphasize the suitability of the suggested models for vehicular applications in real world environment.

Driving toward Connectivity: Vehicular Visible Light Communications Receiver with Adaptive Field of View for Enhanced Noise Resilience and Mobility.

Wireless communication represents the basis for the next generation of vehicle safety systems, whereas visible light communication (VLC) is one of the most suitable technologies for this purpose. In this context, this work introduces a novel VLC receiver architecture that integrates a field-of-view (FoV) adaptation mechanism in accordance with the optical noise generated by the sun. In order to demonstrate the benefits of this concept, a VLC prototype was experimentally tested in an infrastructure-to-vehicle (I2V) VLC configuration, which uses an LED traffic light as the transmitter. At the receiver side, an automatic FoV adaptation mechanism was designed based on a mechanical iris placed in front of a photodetector. Adjustments were made based on the values recorded by a multi-angle light sensor, built with an array of IR photodiodes covering an elevation from 0° to 30° and an azimuth from -30° to 30°. Depending on the incidence of solar light, the mechanical iris can adjust the FoV from ±1° to ±22°, taking into account both the light irradiance and the sun's position relative to the VLC receiver. For experimental testing, two identical VLC receivers were used: one with an automatic FoV adjustment, and the other with a ±22° fixed FoV. The test results performed at a distance of 50 m, in the presence of solar irradiance reaching up to 67,000 µW/cm2, showed that the receiver with a fixed FoV saturated and lost the communication link most of the time, whereas the receiver with an adjustable FoV maintained an active link throughout the entire period, with a bit error rate (BER) of less than 10-7.

Design and analysis of allan variance based adaptive noise canceller for vehicular visible light communication

Design and analysis of allan variance based adaptive noise canceller for vehicular visible light communication

A Survey of Vehicular VLC Methodologies.

Visible Light Communication (VLC) has recently emerged as an alternative to RF-based wireless communications. VLC for vehicles has demonstrated its potential for Intelligent Transportation Systems (ITSs) to exchange information between vehicles and infrastructure to achieve ITS core goals, such as improving road safety, passenger comfort, and traffic flow. This paper seeks to provide a detailed survey of vehicular VLC systems. This paper presents an overview of current developments in vehicular VLC systems and their benefits and limitations for experienced researchers and newcomers.

Design and performance evaluation of vehicular visible light communication system under different weather conditions and system parameters

Design and performance evaluation of vehicular visible light communication system under different weather conditions and system parameters

IRS-assisted vehicular visible light communications systems: channel modeling and performance analysis.

Visible light communications (VLC) is a promising solution as an alternative for the fully occupied radio frequency bands in the near future. The rear (tail) and front of vehicles have lamps that can be used for vehicular visible light communications (VVLC) systems. However, one of the main challenges of VLC systems is the line-of-sight (LoS) blockage issue. In this paper, we propose the installation of intelligent reflecting surfaces (IRSs) (i.e.,smart mirrors) on the back of vehicles to overcome the issue in VVLC systems. We assume three different patterns of angular distribution for the radiation intensity: a commercially available LED with an asymmetrical pattern (Philips Luxeon Rebel), a symmetrical Lambertian pattern, and an asymmetrical Gaussian pattern. In the first section of this paper, we obtain the channel model for the IRS-assisted VVLC systems, then we investigate the path loss results versus link distance under different conditions such as weather type (clear, rainy, moderate fog, and thick fog) and radiation patterns. Moreover, the impact of system parameters such as the aperture size of the photodetector (PD), side-to-side and front-to-front distances, the number of IRS elements, and the IRS area are studied. In the second part, we derive a closed-form expression for the maximum achievable link distance versus the probability of error for the IRS-assisted VVLC systems. In addition, in this section we analyze the impact of the parameters in a single-photon avalanche diode (SPAD), background noise, and the system parameters for the path loss.

(Vehicle’s YB)-based LPB prediction model and anti-LPB (communication link)-reconstruction strategy in the (VLC/RF)-V2X network

The hybrid vehicle-to-everything (V2X) network based on visible light communication (VLC) and radio frequency (RF) ((VLC/RF)-V2X Network) can provide a stable communication network to vehicles. It has great development forward. However, light path blocking (LPB) is a major problem for vehicular visible light communication (V-VLC). It can cause serious communication outage because the visible light signal cannot penetrate opaque obstacles. In view of this, a (vehicle’s yielding behavior (YB))-based LPB prediction model and an anti-LPB (communication link)-reconstruction strategy in the hybrid network are firstly proposed. At first, based on vehicles’ yielding behavior, a LPB prediction model is constructed. By this model, LPB can be predicted before the VLC link is blocked. Next, based on the prediction result of the model, a strategy of restructuring communication links is present. By this strategy, communication links can be self-adaptive changed or supplemented. Then, based on the proposed model and strategy, the anti-LPB scheme is finished. By the scheme, LPB can be avoided timely, communication outages and redundant handovers can be reduced effectively. Finally, by simulations, the model’s validity and the scheme’s effectiveness have been demonstrated. Through LPB prediction and link reconstruction, the proposed scheme avoids LPB caused by user-behavior blockage at source for the first time in multiple road regions. And it has the comparative advantages of faster response time and lower handover number. Compared with other methods, the average advance time of handovers is improved by 66.94% and the average handover number of the network is reduced by 68.48%. What’s more, the path loss (PL) caused by LPBs is reduced by 92% on average.

Vehicle light communication design using an efficient learning model

Vehicle communication is preferable in vehicular visible light communication (VVLC) owing to its low complexity, secure, interference-free characteristics, line of sight exploitation, vehicle light emitting diodes, and vehicle light propagation characteristics. The channels of VVLC are stochastic and give less accuracy during path loss prediction without considering external environmental factors. There is no wireless channel adopted for channel-based frequency response and node multi-access. This work concentrates on modeling a machine learning-based model for VVLC channel modeling and enhancing the accuracy by specifically concentrating on frequency response via multiple variables like environmental factors and vehicle mobility. The proposed model considers variables with the adoption of an Extreme learning model (ELM) with feed-forward neural networks (FFNN). This model performs information processing over the VLC channel to enhance prediction. The accuracy of the proposed model relies on channel modeling and multi-access relays among nodes. The proposed model performance is evaluated with prevailing approaches to produce distance prediction and response among the relay nodes. Some metrics like BER, SNR, MSE, received power, impulse, and frequency response, and received optical power are evaluated and compared with other approaches.

Vehicular Visible Light Communication With Low Beam Transmitters in the Presence of Vertical Oscillation

The availability of light-emitting diodes (LEDs) in vehicle exteriors makes possible the use of visible light communication (VLC) as a vehicle-to-vehicle (V2V) wireless connectivity solution. Although high beam headlights offer higher illumination levels and further communication distances compared to low beam headlights, regulations restrict high beam utilization in many driving cases. These restrictions make low beam headlights a more suitable candidate for vehicular VLC systems. In this paper, we consider two heavy vehicles (e.g., trucks) on a road following each other. Low beam headlights of the follower truck act as wireless transmitters and the lead truck is equipped with a photodetector at its back. We first propose an accurate path loss model based on experimental measurements. The proposed model takes into account the presence of lateral shift between the trucks as well as the fact that headlamps and photodetector can be placed at different heights. Furthermore, we model the truck vertical oscillation experimentally at different speeds. Utilizing these models, we derive a bit error rate (BER) expression for VLC-based truck-to-truck communication system and investigate the effect of several system and channel parameters on the performance. In an attempt to mitigate the degrading effects of the vertical oscillation, we further investigate the proper selection of photodetector location in order to minimize the error rate performance.

A camera-based vehicular visible light communication system using modulated taillights in public road scenarios

This paper proposes a camera-based vehicular visible light communication system using modulated LED taillights for vehicle-to-vehicle communication. The taillights are modulated using on-off keying with a carrier frequency above the critical flicker frequency threshold to appear steady to the human eye and only a camera with a short exposure time can perceive the signal. For receiving the signal, a common camera with a recording frame rate of 30 frames per second was used for the experiments. This limits the throughput of the communication system as only one bit per frame and per individually modulated light source can be transmitted, thus the system is not suitable for transmitting time-critical data. However, the main advantage is that the transmitted data as well as the transmitting vehicle are visible in the camera image, hence we can associate the message and its origin.For the communication between two cooperative autonomous vehicles, e.g., members of a platoon, a secure wireless channel with low latency is needed. To establish an encrypted connection in this main channel our system can be used as an out-of-band channel to verify the identity of the vehicle in front by transmitting a verification code.In this paper we evaluate how the communication quality in terms of bit error rate of the raw data transmission without any error correction methods is influenced by various environmental factors, e.g., communication distance, traveling speed, weather, brightness, etc. This is done by testing our system in controlled scenarios as well as on public roads. The results show that our system is capable of transmitting data with a raw bit error rate of 1.59% on average in platooning relevant situations on the highway in dry conditions. Rain affects the system due to raindrops on the windshield, spray thrown up by vehicles in front, and the windshield wipers occluding the modulated taillights of the transmitting car. In light to medium rain conditions the mean bit error rate is between 2.7% and 6.2%, depending on the intensity.

On the performance analysis of NOMA-based vehicular visible light communication systems

Communication-based vehicle safety applications have emerged as one of the best solutions to enhance road safety. In this area, visible light communication (VLC) has great potential for such applications, named Vehicular VLC (V-VLC). V-VLC is preferred due to its highly secure, low complexity, and radio frequency (RF) interference-free characteristics, exploiting the line of sight (LoS) propagation of visible light and usage of already existing vehicle light-emitting diodes. This research addresses the application of the non-orthogonal multiple access (NOMA) technique in V-VLC based vehicle-to-vehicle communication. In this study, we proposed a system integrating NOMA in V-VLC networks and comprehensively provided an analysis of the system. Subsequently, we derived theoretical achievable capacity and an exact bit error rate expression for the proposed scenario. This paper also covers discussions about system performance under the non-ideal NOAM at the receiver, the effect of transmitter-receiver distance, and the impact of different weather conditions. The derived analytical BER and channel capacity expressions are verified with the simulation results.

Vehicular Visible Light Communication for Intersection Management

An innovative treatment for congested urban road networks is the split intersection. Here, a congested two-way–two-way traffic light-controlled intersection is transformed into two lighter intersections. By reducing conflict points and improving travel time, it facilitates smoother flow with less driver delay. We propose a visible light communication system based on Vehicle-to-Vehicle (V2V), Vehicle-to-Infrastructure (V2I) and Infrastructure-to-Vehicle (I2V) communications able to safely manage vehicles crossing through an intersection, leveraging Edge of Things (EoT) facilities. Headlights, street lamps, and traffic signals are used by connected vehicles to communicate with one another and with infrastructure. Through internally installed Driver Agents, an Intersection Manager coordinates traffic flow and interacts with vehicles. For the safe passage of vehicles across intersections, request/response mechanisms and time and space relative pose concepts are used. A virtual scenario is proposed, and a “mesh/cellular” hybrid architecture used. Light signals are emitted by transmitters by encoding, modulating, and converting data. Optical sensors with light-filtering properties are used as receivers and decoders. The VLC request/response concept uplink and downlink communication between the infrastructure and the vehicles is tested. Based on the results, the short-range mesh network provides a secure communication path between street lamp controllers and edge computers through neighbor traffic light controllers that have active cellular connections, as well as peer-to-peer communication, allowing V-VLC ready cars to exchange information.

Vehicular visible light communications noise analysis and modeling.

Vehicular visible light communications (VVLC) is promising intelligent transportation systems technology with the utilization of light-emitting diodes. The main degrading factor for the performance of VVLC systems is noise. Traditional VVLC systems noise modeling is based on the additive white Gaussian noise assumption in the form of shot and thermal noise. In this paper, to investigate both time correlated and white noise components of the VVLC channel noise, we propose a noise analysis based on Allan variance, which provides a time-series analysis method to identify noise from the data. The results show that white noise and random walk are observed in the VVLC systems. We also propose a motion detection algorithm based on the adaptive Gaussian mixture (GM) model to generate a double Gaussian model of VVLC channel noise. We further present a study on the error performance of a VVLC system considering channel noise to be a mixture of Gaussian components. We derive the analytical expressions of probability of error for binary phase-shift keying and quadrature phase-shift keying constellations. It has been observed that, in the presence of GM noise, the system performance degrades significantly from the usual one expected in a Gaussian noise environment and becomes a function of the mixing coefficients of the GM distribution.

A Review–Unguided Optical Communications: Developments, Technology Evolution, and Challenges

This review paper discusses the complete evolution of free-space optical (FSO) communication, also known as unguided optical communication (UOC) technologies, all the way back to ancient man’s fire to today’s machine-learning-supported UOC systems. The principles, significance, and developments that have happened over the past several decades, as well as installation methodologies, technological limitations, and today’s challenges of UOCs are presented. All the subsets of UOC: FSO communication, underwater optical wireless communication (UOWC), and visible light communication (VLC), with their technology/system developments, potential applications, and limitations are reviewed. The state-of-the-art developments/achievements in (i) FSO channel effects and their mitigation techniques; (ii) radio-over-FSO techniques; (iii) wavelength division multiplexing and sub-carrier multiplexing techniques; (iv) FSO for worldwide interoperability for microwave access applications; (v) space optical satellite communication (SOSC); (vi) UWOC; (vii) photoacoustic communication (PAC); (viii) light-fidelity; (ix) VLC; (x) vehicular VLC (V2LC); and (xi) optical camera communication are reviewed. In addition, the current developments on emerging technologies such as artificial intelligence (to improve the performance of UOC systems), energy harvesting (for the effective utilization of UOC channels), and near-future communication network scenarios (mandatory for secured broadband digital links) are covered. Finally, in brief, to achieve the full potential of UOC systems, challenges that require immediate research attention are summarized.

Addressing Multi-User Interference in Vehicular Visible Light Communications: A Brief Survey and an Evaluation of Optical CDMA MAC Utilization in a Multi-Lane Scenario.

Visible Light Communications (VLC) are developing as an omnipresent solution for inter-vehicle communications. Based on intensive research efforts, the performance of vehicular VLC systems has significantly improved in terms of noise resilience, communication range, and latencies. Nevertheless, in order to be ready for deployment in real applications, solutions for Medium Access Control (MAC) are also required. In this context, this article provides an intensive evaluation of several optical CDMA MAC solutions and of their efficiency in mitigating the effect of Multiple User Interference (MUI). Intensive simulation results showed that an adequately designed MAC layer can significantly reduce the effects of MUI, ensuring an adequate Packet Delivery Ratio (PDR). The simulation results showed that based on the use of optical CDMA codes, the PDR can be improved from values as low as 20% up to values between 93.2% and 100%. Consequently, the results provided in this article show the high potential of optical CDMA MAC solutions in vehicular VLC applications, reconfirm the high potential of the VLC technology in inter-vehicle communications, and emphasize the need to further develop MAC solutions designed for such applications.

Increasing Vehicular Visible Light Communications Range Based on LED Current Overdriving and Variable Pulse Position Modulation: Concept and Experimental Validation

Due to its unique advantages, the integration of Visible Light Communications (VLC) in vehicle safety applications has become a major research topic. Nevertheless, as this is an emergent technology, several challenges must be addressed. One of the most important of these challenges is oriented toward increasing vehicular VLC systems' communication range. In this context, this article proposes a novel approach that provides a significant communication distance enhancement. Different from most existing works on this topic, which are based on refining the VLC receiver, this new article is focused on improving the VLC system based on the benefits that can be achieved through the VLC transmitter. The concept is based on Light-Emitting Diode (LED) current overdriving and a modified Variable Pulse Position Modulation (VPPM). Therefore, LED current overdriving provides the VLC receiver higher instantaneous received optical power and improved Signal-to-Noise Ratio (SNR), whereas the use of the VPPM ensures that the VLC transmitter respects eye regulation norms and offers LED protection against overheating. The concept has been experimentally tested in laboratory conditions. The experimental results confirmed the viability of the concept, showing an increase of the communication range by up to 370%, while maintaining the same overall optical irradiance at the VLC transmitter level. Therefore, this new approach has the potential to enable vehicular VLC ranges that cover the requirements of communication-based vehicle safety applications. To the best of our knowledge, this concept has not been previously exploited in vehicular VLC applications.

Aligning the Light for Vehicular Visible Light Communications: High Data Rate and Low-Latency Vehicular Visible Light Communications Implementing Blind Interference Alignment

Vehicle-to-vehicle (V2V) communications are one of the most promising 6G scenarios. However, V2V communications demand high data rates and extremely low-latency requirements that are difficult to satisfy nowadays. Recently, vehicular visible light communications (V-VLC) have been proposed as a promising technology to guarantee such requirements. Multiple-input, multiple-output (MIMO) techniques can potentially achieve high data rates. However, when applied to V-VLC, they confront challenges such as the latency because of the need for closed-loop transmission or the correlation among optical channel responses. This article explains the use of blind interference alignment (BIA) for V-VLC based on the concept of a reconfigurable photodetector to provide linearly independent channel responses. It is shown that BIA solves the issues of MIMO techniques and may comply with the 6G V-VLC requirements. Besides, the vehicles are a convenient platform for implementing a reconfigurable photodetector. Finally, the open issues for BIA implementation in V-VLC are discussed to inspire future research.

A Comprehensive Investigation on Multi-User Interference Effects in Vehicular Visible Light Communications.

Vehicular visible light communications (VLC) are considered a suitable technology for vehicular platooning applications. Nevertheless, this domain imposes strict performance requirements. Although numerous works have shown that VLC technology is compatible with platooning applications, existing studies are mainly focused on the physical layer performances, mostly ignoring the disruptive effects generated by neighboring vehicular VLC links. Nevertheless, the 5.9 GHz Dedicated Short Range Communications (DSRC) experience has shown that mutual interference can significantly affect the packed delivery ratio, pointing out that these effects should be analyzed for vehicular VLC networks as well. In this context, this article provides a comprehensive investigation focused on the effects of mutual interference generated by neighboring vehicle-to-vehicle (V2V) VLC links. Therefore, this work provides an intensive analytical investigation based on simulation and also on experimental results that demonstrate that although ignored, the influence of mutual interference is highly disruptive in vehicular VLC applications. Hence, it has been shown that without preventive measures, the Packet Delivery Ratio (PDR) can decrease below the imposed 90% limit for almost the entire service area. The results have also shown that although less aggressive, multi-user interference affects V2V links even in short-distance conditions. Therefore, this article has the merit of emphasizing a new challenge for vehicular VLC links and points out the importance of multiple-access techniques integration.

Enhancement of Vehicular Visible Light Communication Using Spherical Detector and Custom Lens Combinations

Vehicular Visible light communication (VLC) technology has recently attracted much interest from researchers and scientists. This technology enables connectivity between vehicles and infrastructures along the road by using vehicles’ headlights and taillights as wireless transmitters. The reliability of vehicle-to-vehicle (V2V) VLC systems is affected by several factors, such as car mobility, optics system design, and visibility conditions, where the first two have the most impact on the VLC system performance. This paper, therefore, focuses on the relative positions of the cars and the design of the optics, especially on the receiving end, which has been proposed with the use of a polar detector instead of the rectangular detectors commonly used in the literature. We investigate the achievable gain compared to the conventional detector for different vehicle locations, utilizing a professional optical system design and ray tracing approach. Then, to improve the performance, we introduce the utilization of an imaging receiver by integrating the polar detector with different optical commercial lens combinations, such as Fresnel and Aspherical lenses. To further improve the V2V system performance, we propose a novel optical lens combination design by integrating double-convex lens with half-Plano-concave lens, which allows the correction of more optical aberrations, such as chromatic and spherical aberration. Utilizing the non-sequential ray tracing tools, we designed these VLC systems and perform a realistic channel modeling study considering the typical 3D CAD models of vehicles and roads as well as the possibility of horizontal and vertical movement between the vehicles. Based on the channel impulse responses (CIRs) obtained from the ray tracing simulations, we analyzed the performance of V2V VLC systems with all lens combinations at different vehicle positions on the road. We further investigated the impact of different system parameters on the overall V2V system performance, such as receiver diameter and bandwidth. The obtained results demonstrated that with a carefully chosen system and lens parameters, the proposed system design of lens combination provides an enhancement of up to 7 dB in total received power compared to the case without a lens. Our results also revealed that the proposed system design outperforms the benchmark ones for all lateral displacements and longitudinal distances.